The overall aim of our research program is to contribute toward an understanding of the structure and biological activity of immunoglobulins. In line with this overall objective we are carrying out the following projects: 1. The structure and properties of an unusual myeloma protein. The crystallizable IgG1 myeloma protein "Dob" apparently has a limited deletion of the hinge region of the heavy chain. We are now carrying on studies to determine the exact location ad extent of the deletion. We will then examine the physical-chemical properties of the molecule to determine the effects of the absence of the hinge region on the conformation and biological properties of this protein. 2. The immune response in tadpoles and frogs. We are studying the immune system in the amphibian, Rana catesbeiana, from several points of view: 1) The isolation and characterization of the immunoglobulins in the adult bullfrog and in the developing tadpole. To date, one "high molecular weight" and two antigenically distinct "low molecular weight" immunoglobulins have been isolated in the adult bullfrog. All of these immunoglobulins are also present in relatively "mature" tadpoles. We are now studying younger tadpoles to determine whether there is a sequential appearance of the immunoglobulin classes during development. The relationship of these proteins to the mammalian immunoglobulin classes is also under investigation. 2) A characterization of the types of lymphocytes in frog blood according to the presence of surface immunoglobulins and responsiveness to mitogens. 3) A study of the frog complement system.